1. Field of the Disclosure
The disclosure relates generally to media processing devices, and, more particularly, to method for minimizing printing defects due to missing nozzles in media processing devices.
2. Description of the Related Art
Media processing devices, such as inkjet printers, are commonly used to print a textual and/or a graphical data on a media sheet. A typical inkjet printer utilizes at least one printhead having a plurality of nozzles configured thereon. Each nozzle of the plurality of nozzles may be configured with an activation resistor and a bubble chamber adapted to receive ink therein. Each nozzle may be “fired” by means of activation resistors, such that a corresponding activation resistor of the nozzle heats the ink in the corresponding bubble chamber of the nozzle. The ink heats up to form an ink bubble in the bubble chamber. The ink bubble is expelled out of the nozzle on to a media sheet, thereby forming an ink dot on the media sheet. The printhead may be moved across (known as a “pass”) the media sheet during which the plurality of nozzles may be selectively fired to print a textual and/or a graphical data on the media sheet.
Typical inkjet printers utilize various print modes based on design of the printhead and the media sheet being printed. Such print modes are typically designed to provide an optimal balance between print quality and print speed. For example, a default print mode, such as “Plain-paper, Normal Mode” emphasizes on good print quality at a fast speed on a plain media sheet. This often requires the number of printhead passes to be minimized while still being able to minimize the visibility of print defects caused by imperfections in the printhead and printing mechanism. One such defect, referred to as dry-time banding, is the result of printing bidirectional in multiple passes. In such a mode, the drying time for the ink on one side of a printed region is longer than the other side before another pass of the printhead places more ink on top of the region. This variable drying time results in a visible color difference on the ends of the printed regions. In particular when adjacent printed areas exhibit inconsistent dry-time, the associated visible defect is quite severe. Various conventional inkjet printers are known to incorporate solutions to the dry-timing banding defect.
One such conventional inkjet printer incorporates one pass bi-directional printing to avoid dry-time banding defects while printing. Because all ink is laid down in a single pass, dry-time banding is avoided. However, this type of print mode is susceptible to color-order defects, which are differences in color for swaths printed in one direction compared to the other direction. This color difference is caused by the printhead physically printing, for example, cyan then magenta then yellow to create a desired color in one direction. In the other direction, the printhead prints yellow then magenta then cyan to create a desired color. However, because the lay-down order of the colorants is different between directions, the mixture may result in different colors after it has dried and cause a color-order print defect that may present as a type of visible banding. This defect may be avoided by providing redundant ink channels (e.g. cyan->magenta->yellow->magenta->cyan) and printing with the required ink channels in each direction to achieve the same color order. This type of system requires additional cost due to the additional ink channels.
Another conventional inkjet printer incorporates two pass bi-directional printing with no paper movement between consecutive passes, followed by a movement of the printhead. Accordingly, same area on a media sheet is printed twice such that the area achieves a consistent color order. Moreover, the conventional inkjet printer achieves a consistency of time between passes that eliminates dry-time banding defects.
However, the conventional inkjet printers as described herein are not capable of avoiding printing defects occurring due to nonfunctional nozzles or blocked nozzles (hereinafter interchangeably referred to as “missing nozzles”). Specifically, some nozzles of the plurality of nozzles of a printhead may become blocked due to dried ink or due to deposition of some particulate matter therein. Moreover, the nozzles may be nonfunctional due to malfunctioning activation resistors thereof. Further, the number of missing nozzles may increase over a lifetime of the printhead.
While printing with a printhead having missing nozzles, desirable print quality may not be achieved due to missing ink drops corresponding to the missing nozzles. Such a printing defect may be observed in print quality of the conventional inkjet printers. Specifically, in the conventional inkjet printers a particular row of ink drops on the media sheets is printed by a distinct set of nozzles of the plurality of nozzles only. Accordingly, a media sheet printed by a printhead having missing nozzles may have missing ink drops even when a bi-directional printing is utilized for printing each row of ink drops on the media sheet. Additionally, upgrading inkjet printers towards permanent and semi-permanent printhead technology requires reducing printing defects due to missing nozzles to obtain acceptable print quality.
Based on the foregoing, there is a need to minimize printing defects while printing with a printhead having missing nozzles. Specifically, there exists a need for a method for printing a media sheet by a printhead such that the method minimizes printing defects on the media sheet due to missing nozzles in the printhead.